Tanks and TRUE volume

[Vivid-Dawn]

I’ve noticed something, and wondering if it’s just me or if this really is a true situation!
My 10 gallon tank only holds 8 (any more, and it will overflow!). My 14 quart buckets for water changes only hold 12 quarts (any more, and they’ll overflow!). My 3 gallon fish tank, only holds two and a half...or overflow, yet again.

So... I have this tank labeled 210 gallons. I have a whole list of fish I want to get, and balanced it so there’s two gallons per inch (yes, I know, that’s not a hard-fast rule, but that’s why I doubled it)... now I wonder if I’m gonna have to re-do my calculations.

I measured my 10 gallon tank, where only the water is. I got the sum of 8 gallons after all. So I did this with my huge tank, measuring only where the water would go... inside the glass, and not quite to the top so the filters could have some room to flow out. This ended up being 145 gallons to 165 if I messed around with the height of the water level a bit (I also figure those containers - as it’s fitted to be a SW tank - for the filter water might disperse the space, too).

I’m not sure I could keep up with 10% water changes twice a week, for that tank, with so much in there. I assume it’d be better to re-do my fish “wish list”... then again, I do plan on having TONS of plants, and they help keep nitrates down (my fully planted tank of 2 gallons with a dozen fry, is always at 0 for Ammonia, Nitrite and Nitrate, and I only change 10% water once a week).

Would I be okay with slightly overstocking? If I keep the Bala Sharks I want (5 of them, estimated at about 12 inches long), that’s 120 gallons right there. I suppose I could do them in a separate tank. But I so wanted them all together! *sniffle*
Everybody all together, including the Balas, would need 249 gallons... feh. I need my own personal lake! LOL

[mlefev]

I don't have an answer for you, but my tank is about the same. I've gotten 9 gallons in it, and it was dangerously high...like don't jump near it or it will spill over. When they calculate the gallons they're going from the seam and edge at the very top to the very base...and no they don't hold quite as much. I think the best way is to measure the band at the top and find out how many cubic inches that takes away from the volume of the tank (there are conversion charts to find the specific volume to cubic inch mathematics). I've found it to be at least 8% water loss for both my friend's tank and mine. So I would think that's standard loss when accounting for the water. Also if you're using sand and a substrate, you have to account for the volume of water displaced by that also.

[Vivid-Dawn]

Yeah, substrate would also be a factor. But I'm just gonna have black cloth under the tank, with a thin layer of decorative marbles. The plants I want (anacharis) are floaters, so they won't need substrate. I might put some Frill in there, and that's floating too...but I could anchor it down, if I wanted.